Listeriolysin O: This major virulence factor generates pores in phagosome membranes, which allows phagocytosed L monocytogenes to escape into the cytoplasm of monocytes and avoid lysosomal destruction.
Actin-based transcellular spread: The organism hijacks the actin-based cellular motility mechanism of host cells, which allows it to spread to adjacent cells without reentering the extracellular space. This significantly reduces exposure of L monocytogenes to antibodies and phagocytic cells.
Because of these adaptations, antibody- and phagocyte-mediated destruction of the pathogen is impaired; therefore, infections are controlled primarily by the cytotoxic T-cell response.
Respiratory distress, temperature instability within the first few hours of life
Granulomatosis infantiseptica (disseminated granulomas/abscesses in liver and spleen, diffuse skin rash) – high mortality. t
Diagnostics
Treatment
DOC: IV Ampicillin (+/- Gentamicin for synergy).
TMP-SMX if PCN allergic.
Key Contraindication/Resistance: Listeria is resistant to all Cephalosporins (part of the LAME mnemonic for organisms not covered by cephalosporins: Listeria, Atypicals, MRSA, Enterococci).
